Thrombolytic therapy (TT) may reduce mortality from acute myocardial infarction (AMI) by nearly 50% if given very early in the courses of certain types of infarction, perhaps being the most effective single therapy ever devised for AMI. Thus the potential enormous impact of TT on the most common cause of death in this country depends on developing ways to rapidly deliver TT to suitable AMI victims. Indeed TT given too late, or insufficiently selectively, may cause serious complications and incur substantial cost, while accruing little benefit. This multicenter collaborative project's aim is to develop a "thrombolysis predictive instrument" (TPI) for emergency room (ER) and emergency medical service(EMS) use that will optimize outcomes of TT by 1) specifically identifying those patients likely to benefit from TT, and 2) facilitating the earliest possible TT administration. Analogous to our earlier predictive instrument for coronary care unit admission, the TPI will be intended to assist decision-making in acute care clinical settings. Its output will be a recommendation to administer, or not administer, TT to a patient sustaining an AMI. This will be based on a decision analytic model which will calculate a patient's likely net benefit (utility) or receiving TT, based in turn on the computations of multivariate predictive regression models. These outcome predictive instruments will predict respectively; 1) acute mortality; 2) severity of cardiac damage (as evidenced by reduction in left ventricular ejection fraction (LVEF); and 3) complications of TT. For real-time use, the TPI will be programmed into a computer-assisted self-interpreting electrocardiograph, or a hand-held calculator, into which features of the patient's immediate clinical presentation are entered, which will result in a real-time recommendation to treat, or not treat, with TT. Additionally, based on our Thrombolysis and Angioplasty in Myocardial Infarction (TAMI) Trial database, we will likely be able to predict a patient's additional benefit to be accrued by use of invasive procedures such as angioplasty in addition to TT. Intended for on-site EMS and ER use, the TPI should promote optimal and early TT treatment decisions, and thereby improve treatment outcomes. Although not utilized by this project, an important by-product will be a set of AMI outcome predictive instruments that could be used for making risk-adjusted outcome comparisons between providers of acute medical care. Indeed, their clinical validity and usefulness should enhance their credibility and acceptance for this use. This project will have 4 phases: 1) developing the TPI component AMI outcome predictive instruments based on data from major trials conducted by the centers involved with this study: The Western Washington Intracoronary and Intravenous Streptokinase Trials, the Myocardial Infarction Triage and Intervention (MITI) Project, the TAMI Trials, and the Acute Ischemic Heart Disease Predictive Instrument Trial; 2) testing of the predictive models on independent data from these same trials, and then harnessing their predictions by use of a decision analytic model so the TPI can provide a recommendation to use or not use TT based on expected net benefit (utility); 3) development and pilot testing of clinically useful implementations of the TPI, specifically in a computer- assisted self-interpreting electrocardiograph; and 4) planning a multicenter prospective clinical trial of the TPI's impact.